Timing apparatus



May 1960 F. BIEDERMAN'N ETAL 2,935,649

' TIMING APPARATUS w, Q W Q h A mm,- m w l w i Q NAN m 8 R m J A mm A m w mm i k F fi 9 mm Q S a Q I N a mm m? m fi H 9 1 1 m. b tlf rlt mm IN V EN TORS Friedrich BIEDERNANN- Richard WICK BY HIGH/7E1. 6. ST

nited States Patent O TllVIlNG APPARATUS 5 Friedrich Biedermann, Unterhaching, near Munich, and Richard Wick, Munich, Germany Application July 1, 1957, Serial No. 668,939

Claims priority, application Germany June 30, 1956 13 Claims. (Cl. 315-241) 15 The present invention relates to a timing apparatus.

More particularly, the present invention relates to an electrical timing apparatus for controlling the time of initiation of current flow through a control tube.

Control tubes such as thyratrons are utilized for electrical timing purposes- Current flow through the control tube is initiated when the potential applied to the control electrode of the tube reaches a preselected potential so that the diiterence between the potential appliedto the control electrode and the potential applied to thecathode of the control tube is a predetermined dilference sufiicient to ignite the tube.

Such apparatus is utilized with photography dark room apparatus, such as photographic enlargers, for example. The initiation of current flow through the tube is made to occur after a desired time period. The time period usually relates to the type of photographic work being done as well as the type of paper or photographic chemicals that are used. 1

There are several difierent types of thyratronsysome being cold cathode tubes and others having heated cathodes. With heated cathodes, the thyratron will ignite when the potential applied to the control electrode is two volts negative with respect to the cathode.

One method of controlling the time period during which the potential applied to the control electrode of the thyratron is increased, is to charge a capacitor connected to the control electrode. The capacitor is charged at a rate proportional to the resistance in the charging circuit and the capacitance of the capacitor. Since the current flow through the tube will be initiated when the control electrode potential is two volts negative with respect to the cathode, it is possible to control thetime period by varying the potential applied to the cathode.

However in any regulation of the cathode voltage it is necessary always to take into consideration the fact that there is a two volt difierential between the potential of the cathode and the potential applied to the control electrode when current flow through the tube is initiated. This two volt diiterential is particularly important when very short time periods are being utilized and also when very small capacitor igniting voltages are utilized. If this two volt differential is not taken into consideration it is possible that large timing errors can result.

However, accounting for the two volt difierential leads to many difiiculties since the zone inwhich the cathode potential can be linearly regulated is very small. Therefore in order to change the time period for the initiation of current how by regulating the cathode voltage, it is essential that very sensitive regulation be provided.

The present invention overcomes these disadvantages by providing an auxiliary apparatus connected to one of the electrodes of the control tube. The auxiliary apparatus applies a potential to the electrode to which it is connected to change the potential of this electrode by an amount which automatically adjusts the relationship between the regulated voltage applied to the cathode and 2,935,649 Patented May 3, 1960 2 the charging voltage for the capacitor, which charging voltage is applied to the control electrode.

Accordingly it is an object of the present invention to overcome the disadvantages of the above-described conventional timing apparatus.

A second object of the present invention is to provide a new and improved timing apparatus for controlling the time of initiation of current flow through a control tube.

Another object of the present invention is to provide a new and improved timing apparatus utilizing a control tube, wherein a regulated voltage is applied to the cathode of the control tube.

A further object of the present invention is to provide a new and improved timing apparatus utilizing the initiation of current flow through a control tube wherein a regulated potential is applied to the cathode of the control tube which equals the potential applied to the control electrode of the tube when current through the tube is initiated.

Still another object of the present invention is to provide a new and improved control tube timing apparatus wherein an auxiliary apparatus is provided for changing the potential of one of the electrodes of the control tube by a predetermined amount to automatically adjust the relationship between the regulated voltage applied to the cathode and the voltage applied to the controlled electrode of the control tube.

Yet a further object of the present invention is to provide a control tube timing apparatus wherein a regulating voltage is applied to the cathode of the control tube, the regulating voltage being adjustable by means of two separate potentiometers.

With the above objects in view, the present invention primarily relates to a timingyapparatus for controlling the time of initiation of current flow through a control tube having at least a control electrode, a cathode electrode and an anode electrode. Regulating means are pro vided for supplying a regulating potential. The regulating means is connected in circuit with the cathode electrode of the control tube for applying a regulating potential thereto in such manner that current flow through the control tube is initiated upon application of a potential determined bythe regulating means to the control electrode of the control tube. Energizing means are connected in circuit with the control tube for applying operating potentials to the electnodes thereof. Finally, control means are connected in circuit between the energizing means and the control electrode for changing the potential applied to the control electrode at a predefined rate in such manner that the potential applied to the control electrode reaches the value predetermined by the regulating means after a desired time period.

In a preferred embodiment, an auxiliary apparatus is connected to one electrode of the control tube. The auxiliary apparatus includes a direct current source and a resistor connected in parallel therewith so that the direct current source produces a voltage across the resistor. The voltage produced across the resistor is applied to the electrode connected to the auxiliary apparatus to increase the potential of this electrode and thereby determine the preselected potential of the control tube at which poten- Y tial the current flow through the control tube will be initiated.

The arrangement of the present invention is such that the preselected potential of the control electrode which initiates current flow through the control tube will be exactly equal to the regulating potential supplied by the regulating means.

In another preferred embodiment of the present invention the direct current source used to produce a voltage across the resistor connected to the electrode of the control tube is produced by utilizing a rectifier in circuit with the alternating current cathode heating circuit of the control tube. This cathode heating current is rectified by the rectifier and produces a direct current voltage across the resistor connected in parallel with the rectifier.

Another preferred embodiment of the present invention includes a relay which is energized when current flow through the control tube is initiated. The relay includes contacts which operate to properly connect the capacitor charging circuit and the voltage developed across the resistor connected to the direct current source.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of a specific embodiment when read in connection with the accompanying drawing. i

The attached drawing is an electrical schematic diagram of one embodiment of an apparatus incorporating the principles of the present invention.

Referring to the drawing, it can be seen that conduc-v tors 1 and 2 are provided for supplying alternating current power to the apparatus. The conductors 1 and 2 may be connected to the ordinary house current, for example.

Connected across the current supply conductors 1 and 2 is the primary winding of a transformer 3. The trans former 3 has a first secondary winding 3 connected to the input terminals of a full-wave rectifier 4. One output terminal 41 of the full-wave rectifier 4 is connected to the electrical ground while the second output terminal 42 is connected by means of a conductor 43 to a'filtering circult.

The filtering circuit is made up of the capacitors 5 and 7 and the smoothing choke 6. Accordingly, the output of the filtering circuit appearing between the conductors 8 and 9 is a direct current voltage which'is produced by the rectification and filtering of the alternating current voltage applied to the primary winding of the transformer 3.

Connected between the conductors 8 and 9 is a resistor 19 which in turn is connected in series with a voltage regulating or stabilizing tube 11. The voltage regulating tube 11 is a conventional tube which has a constant volt age drop thereacross regardless of the potential applied across the terminals thereof. Y

The resistor 10 and the tube 11 have a junction point 26 therebetweeri which is connected to one end of a potentiometer 29 having a'variable tap 44. The other end of the potentiometer 2 9 is connected to the conductor 9 by means of a resistor 31. The adjustable tap 44 of the potentiometer 29 is in turn connected to one end of a second potentiometer 30 having an adjustable tap 46. The other end of the potentiometer 30 is connected to the electrical ground conductor 9 by means of the resistor 32.

The junction 26 is also directly connected by means of a conductor 47 to a fixed contact 28which is shown making electrical contact with a movable armature 27. In another position of the armature 27, the same can make electrical contact with a second fixed contact 33 which is connected to one end of a resistor 34. The other end of the resistor 34 is connected to the adjustable tap 46 of the potentiometer 3,0 and is'also connected by means of a conductor 48 to the junction point between a half-wave rectifier 35 and a capacitor 36.

The other side of the're ctifier 35 is'connected to a conductor 18 which forms one conductor of the alternating current used for heating the cathode of a control tube 13. The other alternating current conductor for heating the cathode is the conductor 17 which is connected directly to the cathode 12 of the tube 13 as well as to the other end of the capacitor 36 and to the movable armature 27.

It can be seen that the alternating current used for heating the cathode of the tube 13 is derived from a second secondary winding 49 of the transformer 3.

The control tube 13 also includes a screen grid 39 which is directly connected to the cathode 12 and an anode electrode 15 which is directly connected to one side of a relay windin 14. The other side of the relay winding 1.4 is connected to the conductor 8.

The anode 15 of the tube 13 is also directly connected by means of a conductorSl to a fixed contact of a pushiutton switch 16, the other fixed contact of which is connected to the movable armature 27. The control tube 13 further includes a control electrode 23 which is connected to one terminal of a resistor 22, the other terminal of which is connected to the fixed contact of a switch 25, one terminal of a capacitor 24 and one electrode of a photoelectric tube 21.

'The other terminal of the switch 25 and the other terminal of the-capacitor 24 are connected to ground. The other electrode of the photoelectric tube 21'is connected to a junction point 53 between a voltage divider made up of resistors 19 and 20. It can be seen that the resistors 19 and 26 are connected in series between the supply conductor 8 and the electrical ground.

The drawing also shows a separate apparatus connected across the supply conductors 1 and 2. This separate apparatus includes a light source 37 connected in series with a switch 38. The light source 37 may be the light source which is used with the photographic apparatus, the operation of which is to be timed by the timing circuit utilizing the control tube 13. It can be seen that the light source 37 will be energized when the switch 38 is in circuit-closing position and deenerg iz ed when the switch 38 is in circuit-opening position.

. The relay winding 14 which is connected to the anode 15 of the control tube 13 controls the switches 25, 27 and'38. That is, the switches 25, 27 and 33 each include movable armatures which are attracted towards the energized relay winding 14 and which are returned by springs, not shown, to a normal position when the relay winding 14 is deenergized. In the illustrated position, the relay winding 14 is energized and accordingly the positions of the switches 25, 27 and 3% correspond to the armature positions when the relay winding 14 is in energized condition. It is accordingly seen that in normai 01' deenergized condition of the relay winding 14, the switch 25 is normally open, the switch 38 is normally closed, and the switch 27 is positioned with the armature thereof making electrical contact with the fixed contact 33.

The push-button switch 16 is preferably arranged on the housing of the apparatus whose operation is to be controlled. When the apparatus is a photographic enlarger, for example, the push-button switch 16 may be arranged adjacent the housing of the enlarger in the region where the photographic paper on which the enlargement 'is to be made is to be inserted. When the cover of the housing is closed, the switch 16 is opened. When the cover is raised to remove exposed photographic paper or to insert new photographic paper, the switch 16 has the illustrated closed position.

In operation, with the cover of the auxiliary photographic apparatus raised, the switches each have their respective illustrated positions. The control tube 13 is not conducting because the switch 16 short circuits the same by being directly connected between the cathode and the anode thereof. The switch 25 short circuits the capacitor 24, to completely discharge the same. The switch 38 is maintained in circuit-opening position so that the light source 37 is not energized.

These illustrated positions, as mentioned hereinabove. correspond to the energized condition of the relay. i can be seen that the relay winding 14 is energized with the switches in the illustrated positions since one terminal ses me thereof is directly connected to the conductor 8 while the other terminal thereof is connected to the electrical ground or conductor 9 by means of the conductor 51, the closed switch 16, the switch 27 and fixed contact 28 and the otentiometers 29 and 30 connected in parallel.

When the cover of the photographic apparatus is closed after a new photographic paper has been inserted, the push-button switch 16 is operated by the cover into its circuit-opening position. This opens the energization circuit for the relay winding 14 thereby deenergizing the same. Accordingly, the switch 38 is moved into circuit-- closing position, the switch 25 is moved into circuitopening position and the switch 27 is positioned with the armature thereof in contact with the fixed contact 33.

When the switch 25 is moved into circuit-opening position, the capacitor 24 is charged through the resistor 19 and the photoelectric cell 21. The photoelectric cell 21 is arranged to be illuminated by the rays emanating from the light source 37. Accordingly the resistance of the tube 21 will depend upon the brightness or the amount of light rays emitted by the source 37 and transmitted through the negative to be printed. Therefore the charging rate of the capacitor 24 is automatically regulated by the intensity of the light falling upon the photoelectric cell 21-.

, It'can be seen that as the capacitor 24 is charged, the potential of the' control electrode 23 connected thereto will increase since this control electrode is connected to the terminal of the capacitor 24 being charged. When the photoelectric cell 21 has reached a predetermined quantity of light emitted by source 37, and, therefore, the potential across the capacitor 24 has'reached a preselected potential, the control tube 13 willbe ignited and current will fi-ow through the tube. When current flows through the tube, the relay winding 14 will be energized Y and the switch 25 will be closed, the switch 27 will be moved into contact with the fixed contact 28 and the switch 38 will be opened. The relay winding 14 will current flow therethrough initiated when the control electrode reaches a preselected potential. This preselected potential depends upon the potential applied to the remaining electrodes of the control tube 13. Particularly, in heated thyratrons, for example, the potential of the control grid for initiating current flow should be about two volts negative with respect to the cathode potential. In the circuit of the accompanying drawing, while the capacitor 24 is being charged it can be seen that the potential of the cathode 12 is determined by the settings of the pctentiometers 29 and 30. Before the control tube 13 is ignited, and while the capacitor 24 is charging, the switch 27 is arranged with the armature thereof in contact with the fixed contact 33. Accordingly the cathode 12 is connected to the adjustable tap 46 of the potentiometer 30 through the resistor 34. It can be seen that the resistor 34 is connected in parallel with a direct current source made up of the rectifier 35 and the capacitor 36 in circuit with the A.C. conductors 17, 18. Accordingly the direct current source will produce a voltage across the resistor 34 depending upon the amplitude of the direct current voltage produced by this direct current source.

The resistance of the resistor 34 is chosen in accordance with the voltage amplitude of the known alternating current heating supply for the cathode. With the proper resistance, the voltage developed across the resistor 34 can be made to be equal to two volts. The direction of current flow determined by the rectifier 35 is arranged so that these two volts are added to the potential of the cathode 12 as determined by the tap 46 of the potentiometer 3d.

" Therefore, the cathode 12 has a potential applied thereto which is exactly two volts higher than the voltage developed at the adjustable tap 46 of the potentiometer 30. Since the control tube will have current fiow initiated therethrough when the potential of the control electrode is two volts negative with respect to the cathode, it is apparent that when the tube 13 is ignited, the potential of the control electrode which is the preselected potential will be exactly equal to the potential at the adjustable tap 46 of the potentiometer 30. In this way it is an easy matter to accurately adjust and calibrate the position of the tap 46 to produce different timing periods.

By adjusting the taps 44 and 46, it is possible to vary the timing periods for the energization of the light source 37. This timing period will correspond precisely to the time period between the opening of the switch 16 to deenergize the relay 14 and the igniting of the tube 13 to energize the relay 14. This time period is determined by the settings of the taps 44 and 46 since the settings of these taps will determine the cathode potential. The potential'of the cathode 12 in turn determines the preselected potential at which the control electrode will initiate current flow through the tube.

' It is accordingly seen that the present invention is practiced by providing an auxiliary apparatus consisting of the direct current source and the resistor 34, which auxiliary apparatus is arranged to change the potential of an electrode of the control tube 13 so that when current flow is initiated through the control tube 13 the potential across the capacitor and applied to the control electrode 23 will be precisely equal to the regulated potential supplied at the tap 46.

It is of courseapparent that if in other tubes another difference of potential is required between the control electrode and the cathode for ignition purposes than the above mentioned two volts, the resistance of the resistor 34 can be properly calibrated to provide such potential difference.

When a linear potentiometer is used for the potentiometer 30, it is clear that the time period between opening of the switch 16 and igniting of the tube will be proportional to the setting of the adjustable tap of the potentiometer.

It is also clear that the resistor 34 can be connected in parallel with a wholly separate direct current source not dependent on the alternating current heating supply for the tube. Similarly, the resistor 34 can be connected between the capacitor 24 and the control electrode 23.

In this way, the potential of the control electrode at ignition of the tube can still be two volts less than the cathode potential while the potential across the capacitor 24 is equal to the regulated potential supplied at the tap 46 of the potentiometer 30.

-In the described embodiment, the regulated voltage for the cathode 12 is produced across the regulating tube 11. However, it'is apparent, that a separate regulated supply can be used for this purpose.

The apparatus illustrated in the accompanying drawing is very flexible since the apparatus for regulating the cathode voltage includes two separately adjustable Potentiometers.

In accordance with the present invention, the capacitor voltage also corresponds to the regulating potential supplied at the tap 46 of the potentiometer 30. This is true even when very small cathode biasing potentials are used and accordingly the range of operation of the oath ode is always linear even when small voltage values are used and when very short timing periods are utilized.

It will be understood that each of the elements described above, or two or more together, may also find a useful application inother types of timing apparatus differing from the types described above, for instance in timing apparatus using no photoelectric cell. Difierent timing periods sensitivity values of the printing paper "2' etc. may be adjusted by adjusting the potentiometers 29, 30.

While the invention has been illustrated and described as embodied in timing apparatus for controlling the time of initiation of current flow through a control tube, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit ofthe present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without emitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims. 7

What is claimed as new and desired to be secured by Letters Patent is:

1. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring aspecific potential difference between said control and cathode electrodes for initiating current flow through said tube regulating circuit means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a preselectedpotential thereto in such manner that current flow through said control tube is initiated upon application, to said control electrode, of a potential determined by said regulating means, but diifering'from said preselected potential by said potential difference; energizing means connected in circuit with said control tube for applying operating potentials to said electrodes thereofg and control means connected in circuit between said energizing means and said control electrode for changing the potential applied to said control electrode at a predefin ed rate in such manner that the potential applied to said control electrode reaches the value differing by said potential difference from said preselected potential determined by said regulating means, after a desired time period.

2. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring a specific potential difference between said control and cathode electrodes for initiating current flow through said tube regulating circuit means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a preselected potential thereto in such manner that current flow through said control tube is initiated upon application, to said control electrode, of a different preselected potential; means connected in circuit with one of the electrodes of said control tube for determining said dilferent preselected potential of said control electrode; energizing means connected in circuit with said control tube for applying operating potentials to said electrodes thereof; and control means connected in circuit between said energizing means and said control electrode for changing the potential applied to said control electrode at a predefined rate in such manner that the potential applied to said control electrode reaches said different preselected potential after a desired time period.

3. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring a specific poential difierence between said control and cathode electrodes for initiating current flow through said tube regulatiug circuit means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a preselected potential thereto in such manner that current flow through said control tube is initiated upon application, to said control electrode, of a potential determined by said c: regulating means, but differing from said preselected potential by said potential difference; energizing means connected in circuit with said control tube for applying operating potentials to said electrodes thereof; and a capacitor connected in circuit between said energizing means, and said control electrode and adapted to be charged by said energizing means at a predefined rate for changing the potential applied to said control electrode in such manner that the potential applied to said control electrode reaches the value differing by said potential difference from said preselected potential determined by said regulating means after a desired time period.

4. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring a specific potential difference between said control and cathode electrodes for initiating current flow through said tube regulating circuit means for supplying a regulatable po tential and being connected in circuit with said cathode electrode of said control tube for applying a preselected potential thereto in such manner that current flow through said control tube is initiated upon application, to said control electrode, of a different preselected potential; means connected in circuit with one of the electrodes of said control tube for determining said ditferent preselected potential of said control electrode; energizing means connected in circuit with said control tube for applying operating potentials to said electrodes thereof; and a capacitor connected in circuit between said energizing means and said control electrode and adapted to be charged by said energizing means at a predefined rate for changingthe potential applied to said control electrode in such manner that the Potential applied to said control electrode reaches said different preselected potential after a desired time period.

5. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring a specific potential diflference between said control and cathode electrodes for initiating current flow through said tube regulating means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a selected cathode potential thereto as determined by said regulating means; energizing means connected in circuit with said control tube for applying operating potentials to said electrodes thereof; control means connected in circuit between said energizing means and said control electrode for introducing a control voltage for changing the potential applied thereto at a predetermined rate and for causing initiation of current flow through said control tube when through introduction of said control voltage said potential applied to said control electrode has reached a predetermined value relative to an existing cathode potential; and auxiliary means connected in circuit with said cathode electrode of said control tube for varying said selected cathode potential applied to said cathode electrode of said control tube by an amount equal to said specific potential difference so that at the start of conductivity of said control tube saidcontrol voltage equals said selected cathode potential supplied by said regulating means whereby the absolute value of the control electrode potential required for rendering said control tube conductive is determinable by said regulating means.

6. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring a specific potential difference between said control and cathode electrodes for initiating current flow through said tube regulating means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a selected cathode potential thereto as determined by said regulating means; energizing means connected in circuit with said control tube for applying operating potentials to said electrodes thereintroduction of said control voltage said potential applied to said control electrode has reached a predetermined Value relative to an existing, cathode potential; and auxiliary circuit means connected in circuit with said cathode electrode of said control tube, said auxiliary circuit means including a direct current source and a resistor connected between said regulating-means and said cathode electrode and being connected in parallel to said direct current source for producing a voltage across said resistor, said voltage being added to said selected cathode potential applied to said cathode electrode of said control tube to vary said selected cathode potential appliedto said cathode electrode by an amount equal-to said specific potential diiference so that at the start of conductivity of said control tube said control voltage 1 equals said selected cathode potential supplied by said regulating means, whereby the absolute value of the control electrode potential required for rendering said control tube conductive is determinable by said regulating means.

7. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring a specific potential difference between said control and cathode electrodes for initiating current flow through said tube regulating means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a selected cathode potential thereto as determined by said regulating means; energiz ing means connected in circuit with said control tube for applying operating potentials to said electrodes thereof, said energizing means including an alternating current cathode heating circuit for supplying cathode heating current to said cathode electrode of said control tube; control means connected in circuit between said energizing means and said control electrode for introducing a control voltage for changing the potential applied thereto at a predetermined rate and for causing initiation of current flow through said control tube when through introduction of said control voltage said potential applied to said control electrode has reached a predetermined value relative to an existing cathode potential; and auxiliary circuit means connected in circuit With said cathode electrode of said control tube and including a rectifier connected in circuit with said alternating current cathode heating circuit to provide a direct current source, said auxiliary circuit means also including a resistor connected between said regulating means and said cathode electrode and being connected in parallel with said direct current source for producing a voltage across said resistor, said voltage being added to said selected cathode potential applied to said cathode electrode of said control tube to vary said selected cathode potential applied to said cathode electrode by an amount equal to said specific potential difierence so that at the start of conductivity of said control tube said control voltage equals said selected cathode potential supplied by regulating means, whereby the absolute value of the control electrode potential required for rendering said control tube conductive is determinable by said regulating means.

8. Apparatus as claimed in claizn 6 wherein switching means are connected in circuit between said direct current source and said resistor, said switching means being movable between circuit'closing position wherein said voltage is produced across said resistor and a circuit-opening position wherein no voltage is produced across said resistor; and means for maintaining said switching means in said circuit-closing position thereof only during a desired time period.

9. Apparatus as claimed in claim' 8 wherein said means for maintaining said switching means in said circuit-closi6 ing position is a relay means connected in' circuit with said anode electrode of said control tube for being ener-' gized to move said switching means to circuit-opening position thereof when current flows through said control tube and for being deenergized to move said switching means into circuit-closing position thereof when no current is flowingthrough said control tube.

10. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and'requiring a specific potential difference between said control and cathode electrodes 1 for initiating current flow through said tube energizing meansconnected in circuit with'said control tube for applying operating potentials to said electrodes thereof; regulating circuit means including at least one potenti ometer connected in'circuit with said energizing means for supplying a regulatable potential and being con nected in circuit with said cathode electrode of said con-' trol tube for applying a preselected potential theretoin such manner that current flow through said control tube is initiated upon application, to said control electrode, of a potential determined by said regulating means, but differing from said preselected potential by said potential difference; and control means connected incircuit between said energizing means and said control electrode for changing the potential applied to said control electrode at a predetermined rate in such manner that the potential applied to said control electrode reaches the value differing by said potential diiference from said preselected potential determined by said regulating means, after a desired time period.

11. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and ananode electrode and requiring a specific po tential difference between said control and cathode electrodes for initiating current flow through saidtube regulating circuit means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a preselected potential thereto in such manner that current flow through said control tube is initiated upon application, to said control electrode, of a potential determined by said regulating circuit means; energizing means, but differing from said preselected potential by said potential ditference connected in circuit with said control tube for applying operating potentials to said electrodes thereof; and control means connected in circuit between said energizing means and said control electrode for changing the potential applied to said control electrode at a predefined rate in such manner that the potential applied to said control electrode reaches the value differing by said potential 'difierence from said preselected potential determined by said regulating means, after a desired time period.

12. In a timing apparatus, in combination, a control tube having at least a control electrode, a cathode electrode and an anode electrode and requiring a specific potential difference between said control and cathode electrodes for initiating current flow through said tube regu lating circuit means for supplying a regulatable potential and being connected in circuit with said cathode electrode of said control tube for applying a preselected basic potential thereto in such manner that current flow through said control tube is initiated upon application, to said control electrode, of a difierent preselected potential determined by said regulating means; means, but differing from said preselected potential by said potential difference connected in circuit with said cathode electrode of said control tube for determining said different preselected potential of said control electrodes; energizing means connected in circuit with said control tube for applying operating potentials to said electrodes thereof; and a capacitor connected in circuit between said energizing means and said control electrode and adapted to be charged by said energizing means at a predefined rate for changing the potential applied to said control electrode in such manner that the potential applied to said control elect e reaches said difi ren preselected pntem ti l after a des red time period,

- '13. In "a'tirning apparatus, in QOmbination, a control tube having at least a control electrode, it cathode electrode an an node el ctro e and requiring a sp Potential .diiierence between said control and cathode electrodes for initiating current flow through said tube; energ zing me n o n c e n ircuit with said control tube for pp y pe a n po ntials to said electrodes ther of; eg ting eans fo supp ying a reg latabl potential and being connected to said cathode electrode of said control tube for applying a selected cathode Pocation to said control electrode initiation of current flow through .said control tube; and auxiliary means connected in circuit with one of the electrodes of said control tube for algebraically adding to the operating potential applied to said one electrode of said control tube an amount equal to said specific potential difference so that at the start of conductivity of said control tube said preselected potential of said capacitor applied to said control electrode equals said selected cathode potential supplied by said regulating means whereby the absolute value of the control electrode potential required for rendering said control tube conductive is determinable by said regulating means.

References Cited in the file of this patent UNITED STATES PATENTS V UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent NO. 2 g 3 q Friedrich Biedermann ct a1a It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In .the grant, lines 1 and 2, for "Friedrich Biedermann, of Unterhaching, near Munich, and Richard Wick, of Munich, Germany, read Friedrich Biedermann, of Unterhaching, near Munich, and Richard Wick, of Munich, Germany, assignors to AGFA Aktjiengesells chaft, of Leverkusen-Bayerwerk, Germany, line 11, for "Friedrich Biedermann and Richard Wick, their heirs read AGFA Aktiengesellgga chaft, its successors in the heading to the printed specifi cation, lines 3 and 4, for Friedrich Biedermann, Unterhaching, near Munich, and Richard Wick, Munich, Germany" read Friedrich Biedermann, Unterhaching, near Munich, and Richard Wick, Munich, Germany, assignors to AGFA Aktiengesellschaft, Leverkusem-= Bayerwerk, Germany column 7, lines 25,, 47, and 69, column 8, lines 17, 40, and 69, column 9, line 30, and column 10, lines 12, 36, and 57, after "tube", each occurrence, insert a semicolon Signed and sealed this 18th day of April 1961,

(SEAL) Attest:

ERNEST W0 SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents 

